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Thread: KTM 2T troubleshooting

  1. #1
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    Default KTM 2T troubleshooting

    breaking this out from the dirt bike thread in case anyone who knows doesn't look there.

    2009 KTM 250 XC, 2 stroke.
    Racing last weekend, all was fine, started a segment, felt a tiny change, maybe a bit of friction, then suddenly no power. bogging under throttle, then just died.

    Track side diagnosis was no spark, checked all the obvious things, no Joy, headed home.

    Today i dove in to it.
    Stator cover off and i was right, the nut on the flywheel had backed off too the end of the shaft. i'm assuming this was the friction I was feeling. it probably contacted the stator and caused a surge/short.

    Broke out the multimeter:
    all continuity is good.
    All resistance seems good also (using ranges found online, don't currently have a service manual, ordering one now).
    Tested the coil next and have continuity across the grounds and its good, but there is NO continuity from the CDI input to the plug cap and NO resistance reading.

    To me that sounds like the coil is shot, which is great because its cheap, but in order for a short to GET to the coil, it had to travel through the CDI, which would not be great.

    I HATE just throwing good parts at it trying to fix things. Any way i can test the CDI?

  2. #2
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    Unless I'm reading what you wrote wrong, there shouldn't be continuity between the CDI input to the coil and the plug output from the coil. Internally there are two coils of wire. One goes between CDI input and ground (you should have continuity here, not sure what the resistance should be). The other goes between ground and your spark plug (again, continuity here, not sure of resistance though it should be high if you're probing at the plug end of the spark plug wire). There is not supposed to be any direct connection between the 12v and high voltage ends of the coil except perhaps at the grounds since they are all shared anyway.

  3. #3
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    Quote Originally Posted by soofle616 View Post
    Unless I'm reading what you wrote wrong, there shouldn't be continuity between the CDI input to the coil and the plug output from the coil. Internally there are two coils of wire. One goes between CDI input and ground (you should have continuity here, not sure what the resistance should be). The other goes between ground and your spark plug (again, continuity here, not sure of resistance though it should be high if you're probing at the plug end of the spark plug wire). There is not supposed to be any direct connection between the 12v and high voltage ends of the coil except perhaps at the grounds since they are all shared anyway.
    interesting. a few of the videos i watched had them testing from CDI input to plug wire output, at the very least for resistance, of which i got none. I also didn't have continuity or resistance from one end of the plug wire to the cap (removed from coil).

    New coil and wire are on the way because they are cheap. outside of that, i'm not sure what else could be going on.

    Edit: just looked again. definitely instructions to test resistance from primary lead to plug cap. i had nothing there.
    Last edited by ITGbuDeev; 05-21-2018 at 11:24 AM.

  4. #4
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    I suppose it could be some kind of weird ass austrian coil but I would never have expected a connection between those two points. Nothing between ends of the plug wire could be an issue. Let us know what happens with the new plug and wire.

  5. #5
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    Check the kill switch contacts and grounds as well.
    Team Brown - LRRS #521

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    Quote Originally Posted by makct04 View Post
    Check the kill switch contacts and grounds as well.
    yup, that was all done trackside and confirmed with the multimeter at home. kill switch functions as it should. All contacts and grounds had been cleaned and greased prior to race.

  7. #7
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    The bendix and all the washers are good as well?
    Team Brown - LRRS #521

  8. #8
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    Quote Originally Posted by makct04 View Post
    The bendix and all the washers are good as well?
    Not using the estart. Kicking over.

  9. #9
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    new coil arrived and is installed. There is now spark, but it is not what i would call "Strong" by any means.

    Found an OEM Stator from Motosport is actually much more reasonably priced than the aftermarkets, and its IN STOCK which is the key, because all aftermarkets are not available right now.

    So, i'll get the stator next and replace that since the case is already opened and it's disassembled.

    Last resort will be the CDI. really hoping i don't need that.

  10. #10
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    Stator replaced.

    Super strong spark.

    Bike will not start. Not on choke, fuel, Starting fluid. nothing.

    Compression tested. ~25 kicks = 90psi. barely half of what a healthy motor should have.

    top end kit ordered, along with new pipe and oil seals because the shifter seal started leaking while it has been sitting.

    I'm afraid that there is going to be something seriously wrong in there since it suddenly "went bad" rather than just loosing some punch over time.

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